1. Field of the Invention
The present invention relates to a communication apparatus having a power saving stand-by mode to reduce power consumption during stand-by and a non-ringing call receiving mode to conduct communication without ringing an associated telephone set in receiving a call.
2. Related Background Art
A prior art apparatus of this type such as a facsimile apparatus has a non-ringing call receiving function in which the apparatus automatically determines whether a received call is for image communication or telephone communication without ringing an associated telephone set when the apparatus receives a call, if it is the image communication, the apparatus starts image reception and if it is the telephone communication, the apparatus applies a simulated calling signal to the telephone set (slave telephone set) to make it ring or generates a call sound from a speaker of the image communication apparatus to inform the call to a user. Such a facsimile apparatus is disclosed in U.S. Pat. No. 4,837,806 issued on Jun. 6, 1989 and U.S. Pat. No. 5,317,629 issued on May 31, 1994.
On the other hand, regulations on the power consumption of electronic equipment have recently been issued in many countries. For image communication apparatus, regulations require reduction of power consumption while in the stand-by mode depending on a recording speed. The power saving stand-by mode which suppresses power consumption is referred to as an ESS (energy saving stand-by) mode.
In the above-mentioned facsimile apparatus which has the non-ringing call receiving mode but does not have the ESS mode, an H relay for isolating a telephone set from a line is provided between the telephone set and a CML (communication line) relay which switches the telephone line between a facsimile apparatus (modem) and the telephone set, and a power is supplied to the H relay to keep the H relay in an on-state during the stand-by. Thus, when a call signal (Cl signal) is received from the line, the Cl signal is prevented from being applied to the telephone set and a bell of the telephone set from being rung.
On the other hand, in a facsimile apparatus having the ESS mode, power is supplied only to a minimum of circuits, such as a control circuit (CPU) of a microcomputer, in order to minimize the power consumption during the stand-by and the power supply to drive the H relay is shut down during the stand-by. As a result, once the apparatus is set to the ESS mode, the H relay cannot be turned on during the stand-by and the non-ringing call receiving mode is not realized.